Re: Marvel Mystery Oil
I'd not be putting it in my crankcase. That said, Marvel is a wonderful general-purpose lubricant for just about anything else. I always keep a tin in the garage.
I even used to put it in the piston dampers of my SU and Zenith-Stromberg carbs back in my MG/Triumph/Jag/Morris days. Never found better for such things.
...sT